Pulp screen with internal dilution rotor



March 19, 1963 a. cow: ETAL PULP SCREEN wrru INTERNAL nnu'rxon ROTOR 2 Sheets-Sheet 1 Filed Dec.

&

INVENTORS B COWAN E COWAN ATTORNEYS March 1963 E. COWAN ETAL 3,08 73 PULP SCREEN WITH INTERNAL DILUTION ROTOR Filed Dec. 29, 1960 2 Sheets-Sheet 2 I i i i 2 o9QO T I j INVENTORS B. COWAN I E- CDWAN I :BY 7!" 1' r ATTOR NEYS r d grates P m 3,681,873 Patented Mar. 19, 1963 3,081,873 PULP SCREEN WITH INTERNAL DILUTEGN ROTGR Eliiah (Iowan and Ben (Iowan, both of 5460 Patricia Ave,

Montreal, Quebec, (Ianada Filed Dec. 29, 1960, Ser. No. 79,218

Claims priority, application Canada Nov. 16, 1960 10 Claims. (Cl. 209-473) This invention relates to pulp screens and more particularly to the horizontal type of screen in which the rotor is provided with longitudinally disposed dilution water passages radiating outwardly from the axis of the rotor, whereby the dilution water is delivered at or near the screen for washing of the thickened pulp mat without shock or turbulence and without forcing the rejected slivers and other foreign matter through the screen.

The invention consists essentially in building into the rotor or impeller of a pulp screen a series of longitudinally disposed radiating passages which will carry the dilution water directly to the area of thickened pulp at the inner surface of the screen, whereby the dilution Water will mix in a gentle manner with the pulp so as to wash the pulp fibres and carry them through the screen without at the same time forcing reject material through the screen. The invention is further characterized in that a portion of the unthickened pulp flowing into the screen is permitted to flow radially about the outer surfaces of the internal passages to mix directly with the dilution water at the exit of the internal passages.

The object of the invention is to provide means whereby the dilution water in a pulp screen is delivered at or near the inner peripheral surface of the screen.

A further object of the invention is to provide means whereby a portion of the unthickened pulp in a pulp screen is constrained to flow radially about the outer surfaces of radially disposed dilution water passages.

A further object of the invention is to design the longi tudinal length of the dilution water radial passages to suit the grade of coarseness of the pulp to be treated.

A further object of the invention is to provide means whereby the dilution water for cleaning of the pulp and carrying away of the reject material is kept separate.

These and other objects of the invention will be apparent from the following description and the accompanying drawings in which:

FIG. 1 is a longitudinal vertical section of a pulp screen in which the rotary impeller has a double bladed section forming radial passages directing dilution water close to the inner surface of the screen.

FIG. 2 is a longitudinal vertical section of impeller only, as shown in FIG. 1.

FIG. 3 is an end View of the rotor shown in FIG. 2 and looking in the direction of the arrows 33.

FIG. 4 is partial longitudinal exterior view of the rotary impeller shown in FIG. 2.

FIG. 5 is a modified form of rotor in which the double bladed section is extended in length to near the outlet end of the rotary impeller.

FIG. 6 is a partial vertical section impeller in which the double blades passages are of the same diameter.

FIG. 7 is a partial cross-section in the line 7-7 of FIG. '6

FIG. -8 is an enlarged detail section showing the apertures in the hollow dilution water passage communicating with the radial passages in the rotary impeller.

.FIG. 9 is an enlarged detail section of the two dilution water passages and showing the seal between them.

Referring to the drawings, a typical form of horizontal pulp screen is shown in FIG. 1 of the drawings and the rotary of a screen rotary forming the radial consists of a frame 5, having a pulp inlet 6 and a reject exit 7. An annular screen =8 is mounted in the frame 5 axially parallel about the composite drive shaft 9. The drive shaft 9 with its rotary impeller 11 is rotated within the frame 5 by means of the drive pulley 10.

In FIG. 1 the composite drive shaft 9 is formed of an outer tubular member 12 and a stub shaft 13 projecting from one end of the tubular member 12. The tubular member 12 is journalled in the frame 5 by the bearing 14 while the stub shaft 13 is journalled in the frame 5 by the bearing 15. An open ended tubular member 16 is mounted axially within the tubular member 12. End rings 17 and 18 seal the ends of the tubular member 16 with the inner surface of the tubular member 12 to form an annular passage 19. Dilution water is fed to tubular member 16 through the inlet 20 while dilution water is fed to the annular passage 19 through the inlet 21.

The screen rotary impeller 11 driven by the composite shaft 9 consists of a series of radially disposed blades 22, mounted on the outer surface of the tubular member 12 of the drive shaft. These blades 22 are held in spaced angular position relative to each other by the rings 23 and 24. Each of the blades 22 are cut-out at 2-5 opposite the axial pulp inlet 6a about the stub shaft 13 in order to permit entry of the pulp into the screen the baffle 28.

with the least interference.

A series of blades 26 project radially outwards from the outer surface of the tubular member 12. These blades 26 are disposed, one between each of the blades 22 and extend lengthwise of the impeller from the inner end 25a of the cut-outs 25 for at least a portion of the length of the impeller towards the discharge end of the screen. A pair of annular baffles 27 and 28 are attached to the radial edges of the blades 26 and to the adjacent surfaces of the blades 22 to form radially directed passages 29. Apertures 30 drilled in the surface of the tubular member 12 in the area between the battles 27 and 28 permit the dilution water from the inlet 20 to pass through the tubular member 16 into that portion 31 of the tubular member 12 between the end 13a of the stub shaft 13 and the end ring 17, and thence through the passages 29 to be discharged close to the inner peripheral surface of the screen 8.

The bafiie 27 is provided with apertures 32 located adjacent the tubular member 12 and between the blades 26 defining the passages 29 and the adjacent blades 22 to permit the flow of pulp into the area between the battles 27 and 28 and mix with the dilution water at the exit of the passages 29.

The surface of the tubular member 12 between the baflle 28 and the discharge end of the screen has the perforations 33 to permit dilution water from the inlet 21 to pass through the annular passage 19 into the body of the rotary screen for final washing of the pulp and the carrying away of reject material through the outlet 7.

The spacing between the baffies 27 and 28 will depend greatly on the type of pulp which is to be cleaned. Where the pulp contains a relatively small amount of slivers and other foreign matter the spacing between the baflies can be relatively small as shown in FIGS. 1 and 2 and by the same token the blades 26 need not extend to the full diameter of the rotor. In addition, the diameter of the bafiie 27 can be smaller than the diameter of This permits the relatively clean pulp to flow around the periphery of the bafile 27 and be further cleaned by the dilution water at the exit of the passages 29.

Where relatively coarse pulp containing a large amount of slivers and other foreign matter is to be treated, the

battles 27a and 28a are spread apart as shown in FIG. 5 permitting a greater injection of dilution water into the pulp close to the periphery of the impeller. When the bafiles are spaced apart as shown in FIG. 5, the length of the tubular member 16a is shortened to coincide with the location of the baffle.

In the modification shown in FIGS. 6 and 7 the diameter of the baflles 27b and 28b is increased to coincide with the outer longitudinal edge of the blades 22 and the blades 2612 are also extended outwardly to extend the radial length of the passages 2912.

In the operation of this invention the impeller with its built in dilution passages having first been assembled to suit as near as possible, the grade of coarseness of the pulp to be treated, the pulp is allowed to flow into the screen through the inlet 6 and axially about the shaft 13 towards the first baffle 27. The baffie 27 diverts the larger quantity of the pulp radially outwards towards the inner periphery of the screen 8 where it forms a thickened mass. A portion of the pulp flowing into the screen passes through the apertures 32 in the lbaflle 27 and is diverted radially outwards by the baffie 28. At the same time, dilution water from two separate inlets 20 and 21 is delivered to the interior of the screen. The water from the inlet 20 is fed directly to the internal passages 29 in the impeller and is mixed with both the thickened pulp on the inner peripheral surface of the screen 8 and with the pulp flowing radially outwards between the bafiles 27 and 28. The pulp washed by the dilution water from the passages 29 is gently cleaned and washed through the apertures in the screen 8 while the heavier reject material is permitted to move axially along the surface of the screen to beyond the bafile 28. Further washing of the coarser pulp beyond the baffle 28 is done by the dilution water from the inlet 21 which passes through the apertures 33 into the body of the screen beyond the bafile 28. The pulp fibres remaining are now separated from the reject material and pass through the screen 8 while the reject material is washed through the outlet 7.

The differences in longitudinal length of the internal dilution water passages as shown between FIGS. 2 and 5 permits of the washing out of a maximum of pulp fibres from slivers or other foreign matter in the shortest possible time and without forcing any slivers or foreign matter through the screen. Furthermore, the blending of the dilution water and relatively thin pulp at the periphery of the impeller with the thickened pulp, results in a gentle washing of the pulp and its separation from slivers without forcing of the slivers against and through the screen, wtih sufiicient water in the vicinity of the screen as to wash the slivers along beyond the bafile 28 for final washing and discharging of the reject material through the outlet 7.

What we claim is:

1. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radially outwards from said hollow drive shaft, a pair of baflles set transversely of the axis of the impeller, a second series of blades projecting radially outwards from said hollow drive shaft and located longitudinally of the impeller between said transverse baflles and positioned one between each of said first mentioned blades and forming therewith and with said transverse baflles a series of radiating passages open at their outer ends adjacent the inner surface of the said screen, the said hollow shaft having a series of apertures in its surface area between said bullies and communicating with the said radiating passages and means to supply dilution water to said hollow shaft and said radiating passages.

2. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radial- 1y outwards from said hollow drive shaft, a pair of baflles set transversely of the axis of the impeller, a second series of blades projecting radially outwards from said hollow drive shaft and located longitudinally of the impeller between said transverse bafiies and positioned one between each of said first mentioned blades and forming therewith and with said transverse bafiies a series of radiating passages open at their outer ends adjacent the inner surface of the said screen, the said hollow shaft having a series of apertures in its surface area between the planes of said bafiles and communicating with the said radiating passages, the said baffie adjacent the pulp stock inlet having a series of apertures therethrough permitting a flow of stock into the areas of the impeller bounded by the said battles and said first men tioned blades and the blades forming the walls of said radiating passages.

3. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radially outwards from said hollow drive shaft, a pair of 'baflies set transversely of the axis of the impeller, a second series of blades projecting radially outwards from said hollow drive shaft and located longitudinally of the impeller between said transverse baflles and positioned one between each of said first mentioned blades and forming therewith and with said transverse baffles a series of radiating passages open at their outer ends adjacent the inner surface of the said screen, the said hollow shaft having a series of apertures in its surface, and an open ended tubular member located axially within said hollow shaft, the said open ended tubular member communicating at one end with a dilution water inlet and at the other end with the said radiating passages through the apertures in said hollow shaft.

4. In a pulp screen as set forth in claim-'1, in which the said transverse baffles and radiating passages are located intermediate of the length of the said impeller.

5. In a pulp screen as set forth in claim 1, in which the said second mentioned blades are of less radial length than the first mentioned blades to locate the outlet end of the radiating passages radially inwards from the periphery of the impeller.

6. In a pulp screen as set forth in claim 1, in which the transverse bafile adjacent the stock inlet of the screen is of less diameter than that of the other of the pairof battles, and the open ends of the radiating passages are set at an angle in the plane of the periphery of the pair of baffles.

7. In a pulp screen as set forth in claim 1, in which the transverse baflle adjacent the stock inlet of the screen has a series of apertures therethrough, the said apertures being offset from the said radiating passages.

8. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radially outwards from said hollow drive shaft, a pair of baffles set transversely of the axis of the impeller, the bafile adjacent the stock inlet being of smaller diameter than that of the other of the pair, a second series of blades projecting radially outwards from said hollow drive shaft and between the said pair of baffles and positioned one between each of said first mentioned blades and forming therewith and with said transverse bafiles a series of radiating passages whose open outer ends are disposed at an angle to the axis of the impeller as defined by the peripheral edge of the said bafiles, the said hollow shaft having a series of apertures in its surface area between the planes of said bafiles and communicating with the said radiating passages, the said hollow shaft having a second series of apertures in its surface area beyond the bafile remote from said stock inlet and 3,0 means to feed dilution water separately to the said radiating passages and through the said second series of apertures in the hollow shaft.

9. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radially outwards from said hollow drive shaft, a pair of bafiies set transversely of the axis of the impeller, a second series of blades projecting radially outwards from said hollow drive shaft and between the said pair of baffles and positioned one between each of said first mentioned blades and forming therewith and with said transverse baffles a series of radiating passages whose open outer ends are located at the periphery of the said bafiles, the said hollow shaft having a series of apertures in its surface area between the planes of said baflles and communicating with the said radiating passages, the said hollow shaft having a second series of apertures in its surface area beyond the baffle remote from said stock inlet and means to feed dilution water separately through said hollow shaft to the said radiating passages and through the said second series of apertures in the hollow shaft.

10. In a pulp screen including an annular screen and a rotary impeller, a pulp stock inlet located axially with respect to said impeller, a hollow drive shaft, the said impeller comprising a series of blades projecting radially outwards from said hollow drive shaft, a pair of battles set transversely of .the axis of the impeller, a sec ond series of blades projecting radially outwards from said hollow drive shaft and between the said pair of 'bafiles and positioned one between each of said first mentioned blades and forming therewith and with said transverse baflies a series of radiating passages whose open ends are located at the periphery of the said bafiies, the said hollow shaft having a series of apertures in its surface area between the planes of said 'baflies and communicating with the said radiating passages, the said hollow shaft having a second series of apertures in its surface area beyond the baffle remote from said stock inlet, means to feed dilution water separately through said hollow shaft to the said radiating passages and through said second series of apertures in the hollow shaft, and means to feed a portion of pulp stock into the area between said bafiles alongside said radiating passages.

References Cited in the file of this patent UNITED STATES PATENTS 1,092,389 Quiller Apr. 7, 1914 1,134,304 Westby Apr. 6, 1915 2,246,669 Cowan June 24, 1941 2,752,828 Sandison July 3, 1956 FOREIGN PATENTS 583,098 Canada Sept. 15, 1959 

1. IN A PULP SCREEN INCLUDING AN ANNULAR SCREEN AND A ROTARY IMPELLER, A PULP STOCK INLET LOCATED AXIALLY WITH RESPECT TO SAID IMPELLER, A HOLLOW DRIVE SHAFT, THE SAID IMPELLER COMPRISING A SERIES OF BLADES PROJECTING RADIALLY OUTWARDS FROM SAID HOLLOW DRIVE SHAFT, A PAIR OF BAFFLES SET TRANSVERSELY OF THE AXIS OF THE IMPELLER, A SECOND SERIES OF BLADES PROJECTING RADIALLY OUTWARDS FROM SAID HOLLOW DRIVE SHAFT AND LOCATED LONGITUDINALLY OF THE IMPELLER BETWEEN SAID TRANSVERSE BAFFLES AND POSITIONED ONE BETWEEN EACH OF SAID FIRST MENTIONED BLADES AND FORMING THEREWITH AND WITH SAID TRANSVERSE BAFFLES A SERIES OF RADIATING PASSAGES OPEN AT THEIR OUTER ENDS ADJACENT THE INNER SURFACE OF THE SAID SCREEN, THE SAID HOLLOW SHAFT HAVING A SERIES OF APERTURES IN ITS SURFACE AREA BETWEEN SAID BAFFLES AND COMMUNICATING WITH THE SAID RADIATING PASSAGES AND MEANS TO SUPPLY DILUTION WATER TO SAID HOLLOW SHAFT AND SAID RADIATING PASSAGES. 